Formation of the orthorhombic phase of perovskite crystals with 3d elements has been considered and models of the crystal structures of LaMnO3, LaTiO3, YTiO3, LaVO3, and YVO3 have been constructed. A generalization of the results of previous studies has been performed with allowance for the effect of T-2g distortions. An analysis of local symmetrized distortions has shown that the structure of compounds with Ti3+ and V3+ ions is determined by the "rotational" distortions of the T-1g type (Q(x) , Q(y) , Q(z)); the T-2g distortions are only secondary. At the same time, in LaMnO3 of special importance are Jahn-Teller E-g distortions. All the crystals examined exhibit a strong coupling between the lattice and electronic degrees of freedom, which manifests itself in strong vibronic effects. In particular, the terms of the vibronic Hamiltonian that are quadratic in Q(x) , Q(y) , and Q(z) determine the orbital structure of t(2g) compounds.